Sexual orientation discrimination is discrimination against a person or group on the basis of their sexual orientation or sexual behavior. Sexual orientation discrimination often comes up in the context of employment actions. It usually refers to a predisposition towards heterosexual people, which is biased against lesbian, gay, and bisexual people, among others. It can, however, also be against heterosexual people. A related term is sexual prejudice, a negative attitude toward someone because of her or his sexual orientation. This bias is not the same as homophobia, but rather is the discrimination towards or against certain sexual orientations. Heterosexism suggests that the basis for this bias is not found in the individual per se but rather has a broader cultural or biological basis that results in attitudes weighted in favour of heterosexuality over other sexual orientations. Heterosexism is one form of structural violence.
An earlier definition of this term is: Sexual orientation discrimination is a belief or argument that one sexual orientation or sexual behaviour is inherently superior to some or all others. Usually it comes in the form of heterosexuality being considered the only natural, normal, or moral mode of sexual behavior, and is also used to refer to the effects of that instinct. The word heterosexism has also been proposed to mean essentially the same thing as this form of sexual orientation discrimination. This word has been suggested as an alternative to homophobia, in part because it uses a parallel structure to sexism or racism. The intent of heterosexism is the examination of the cultural bias against non-heterosexuals rather than individual bias, which is the focus of homophobia, as well as the adverse effects of normative heterosexuality on heterosexual identifying people.
In queer theory, heterosexism is closely related to heteronormativity.